Determining the root cause of a neighbouring-cell-interaction-induced latch-up failure event

It has always been a challenge to identify the failure mechanism of electrical overstress and latch-up failures due to misleading failure modes observed from electrical fault isolation. A Latch-up failure event involving an I/O cell of a SoC device is investigated. The root cause is determined by combining failure analysis, layout and commonality studies. It is found that the presence of abutting pad cells guardrings is critical for latch-up immunity.